b'This report provides concise summa-Fabrication trials on reduced-diam-A major ATF-2 test train design ries of many of the significant AFCeter fuel pellets (UO 2and U 3 Si 2 ) weremodification for boiling water reactor accomplishments made during FY-19. success, setting the stage for possible(BWR)-sized rodlets was completed, Of particular note are the accelerated testing in ATR using theandtwelve new test rodlets from following key accomplishments FAST approach. General Electric (GE) are to be and their significance:Progress was made in investigationsintroduced into ATF-2 during theThe Halden Gap Assessment Finalof microstructurally engineered UNoutage preceding ATR Cycle 166B.Report with recommendations toby introducing Y in an attempt to Design of a new 9-pin tier for ATF-2 Department of Energy (DOE) Nuclearimprove its corrosion and oxidationwas completed, which could effec-Energy (NE) on strategies andresistance tively increase the rodlet capacity of investments needed to support testing Fracture toughness measurementsthe ATF-2 test train by 50% (a recom-and qualification of industry-led ATFusing small scale cantilever beammendation included in the Halden concepts without the Halden Reactortesting was performed using unirra- Gap Assessment).was issued in December 2018. diated UO 2and found to be in good Uranium silicide fuels in ATF-1Uranium silicide (U 3 Si 2 ) fuelagreement with data obtained usingreached burnups of ~40 GWd/MTU, pellets fabricated at INL wereconventional testing; this method- the equivalent of two full cycles in a incorporated into fuel rods as part ofology will be extended to irradiatedcommercial power reactor; interim a Westinghouse Lead Test Assembliesfuel specimens in the future.examinations to date have indicated (LTA) loaded into the Byron Variations in minor alloying con- that these silicide fuels exhibit very commercial power reactor, which hasstituent levels were explored in newlow swelling and fission gas release, been operating at full power sinceheats of FeCrAl cladding resultingwhich is a significant improvement April 2019; this represents the firstin improved properties, improvedover conventional fuels under normal DOE-sponsored commercial LTA thatmeasurements of hydrogen diffusionoperations in addition to benefits included a new fuel form. in FeCrAl cladding were obtained,they promise to provide under acci- A vapor phase processing capabilitytube production and characterizationdent scenarios.for advanced SiC/SiC composites wasof ODS FeCrAl variants were initiated, Analyses performed using the BISON established atOak Ridge Nationaland the FeCrAl Properties Handbookfuel performance code showed Laboratory (ORNL) to allow forwas updated and issued. remarkable agreement between fabrication of specimens needed for Prototypic testing of Westinghousepredicted and measured fission gas characterization, optimization, andand Framatome ATF concepts inrelease for the standard UO 2fuels performance testing. Advanced Test Reactor (ATR) 2Aincluded as experiment controls,Fundamental understanding ofLoop (ATF-2) continued throughoutwhich serves to validate the design uranium silicide fuel was extendedFY19, and test fuel rodlets achievedapproach of the ATF-1 test series.through temperature-dependentburnups ~10 GWd/MTU by year Conceptual design of ATR I-Loops neutron diffraction measurements,end. The ATF-2 Loop continues toas recommended in the Halden Gap thermo-mechanical property mea- be the only in-reactor option in theAssessment was initiated, with the surements, and thermodynamicwestern world for testing of ATFobjective of providing prototypic evaluations of U 3 Si 2hydride reactions,concepts under prototypic ReplaceBWR test conditions, ramp testing, and new fabrication and character- with pressurized water reactorand run to failure testing capabili-ization studies on doped UO 2fuel(PWR) conditions. ties needed to qualify ATF concepts concepts were initiated. without the Halden Reactor.2019|AFC ACCOMPLISHMENTS 11'